Project Summary Phosgene is essential to the manufacturing of products used in everyday life such as flexible foams, thermoplastic polyurethane, and sealants and elastomers. It is also a building block for many plastics, pesticides, and pharmaceuticals. However, at room temperature phosgene is an extremely toxic, colorless gas?exposure can cause immediate symptoms of eye and skin irritation, and symptoms of respiratory distress such as coughing, tightness in the chest, difficulty breathing, pneumonia, or heart failure that may not manifest until 6-24 hours after exposure. Therefore, phosgene-producing facilities need large phosgene detectors for wide-area monitoring as well as phosgene indicator badges for monitoring individuals. Electrochemical detectors perform real-time monitoring with audio alarms for phosgene exposure, but they are expensive and can only be installed in limited locations. The wearable colorimetric indicator badge is the standard means of monitoring individuals. It indicates the presence of phosgene by changing color, but the worker must constantly be looking at the badge to ensure safety since the badge does not actively alert the user of danger. Intelligent Optical Systems, Inc. (IOS) proposes to develop a reliable, low-cost wearable phosgene sensor for individuals that will revolutionize how colorimetric phosgene gas badges protect workers by integrating the sensor into the worker's safety goggles, so a colorimetric change reflecting the detection of phosgene in the environment will be immediately apparent to the user.